1. Field of the Invention
This invention pertains to the use of both passive and active balancers for a cryocooler compressor, and to a hydraulically actuated compressor used for pumping fluids, and more particularly to a balanced single stage linear compressor with a free-floating diaphragm used to reduce the wear and tear usually associated with a more conventional piston-type compressor.
2. Description of the Prior Art
In the prior art, it is well known that the use of a transverse piston in a Stirling heat engine or similar apparatus results in a rocking motion about the center of mass of the engine, thereby putting a load on the engine displacer bearings and combustor assembly. In order to counteract these forces, a counterweight can be used as a passive balancer. For example, U.S. Pat. No. 4,450,685 to Corey discloses a hydraulically driven counterweight in a resonant free piston Stirling engine wherein the product of the piston mass and the piston stroke is equal to the product of the counterweight mass and stroke. While such a counterweight configuration counteracts a substantial portion (approximately 99%) of the potential vibration, there is some residual vibration due to losses in the elements and frictional effects.
Other relevant heat engine references include commonly-owned U.S. Pat. Nos. 5,022,229 and 5,109,673 to Vitale.
Similarly, in the prior art, it is known to use a diaphragm compressor, such as from U.S. Pat. No. 5,074,755. But such a configuration has several disadvantages. Firstly, in order to have a balanced system, two compressors are usually operated in an opposed configuration so that the compressors are 180.degree. out of phase with each other.
Secondly, to insure that the two compressors are in fact 180.degree. out of phase with each other, some form of active control on one or both of the compressors is necessary.
Thirdly, since cost is usually a significant consideration in the evaluation of a compressor, the use of two compressors has a distinct disadvantage of being more costly than a single larger compressor.
Finally, the space claim envelope of a balanced back-to-back compressor is larger than that of a single larger compressor.
Other references include U.S. Pat. No. 5,246,351 to Horn et al.; U.S. Pat. No. 5,192,198 to Gebauer et al.; U.S. Pat. No. 5,186,615 to Karliner; U.S. Pat. No. 5,145,331 to Goes et al.; U.S. Pat. No. 5,088,901 to Brauer; and U.S. Pat. No. 4,430,048 to Fritsch.